Wednesday, June 13, 2012

Class XI, BIOLOGY,"The Kingdom Protoctista (Protista)"

It is found attached to rocks, along the sea coast in intertidal zones (the area between the high tide and low tide mark)

In Karachi, it is found on Manora coast.

STRUCTURE

Ulva exhibits primitive simple multicellular organization.

The plant body is a thallus, which is flat, erect , wrinkled and sheet like structure having a length of about 30 cm (1ft).

The thallus is very thin and internally it is composed of two vertical rows of cells only.

Its lower part forms a “hold fast”, consisting of long thread like cells for attachment to the substratum.

REPRODUCTION
Ulva can reproduce sexually as well as asexually. (1)SEXUAL REPRODUCTION

Sexual reproduction is isogamous and takes place in sexual plants or gametophyte, which are haploid (n).

Each cell of the gametophyte produces many biflagellate gametes, which are released in seawater.

The gametes are morphologically similar or isogametes but the fusion
takes place between gametes produce by two different gametophyte
plants, which are termed as positive strain and the negative strain.

ALTERNATION OF GENERATION
A distinct regular alternation of generations between the haploid
gametophytes (sexual plant) and diploid sporophyte (asexual plant) is
present. Since the two plants are morphologically similar so this
process is known as “Alternation of generation (isomorphic)”CHLORELLA
FIGURE 7.2 PAGE # 127.OCCURANCE

Chlorella is a fresh water alga found floating in stagnant water of ponds, pools and ditches.

It is easily cultured and has been used an experimental organism in research in photosynthesis.

STRUCTURE

The body of chlorella is one celled, spherical in outline and solitary.

It contains a single nucleus and a cup-shaped chloroplast usually with out pyrenoid.

REPRODUCTION (ASEXUAL REPRODUCTION)

Reproduction takes place by aplanospore formation, which involves the division of protoplast into 8-16 daughter protoplast.

Each daughter protoplast secrets a wall to produce a non-motile aplanospore.

On release from the parent cell, each aplanospore forms a new vegetative cell.

IMPORTANCE
Recently an antibiotic known as “Chlorellin” useful for the control of bacterial diseases has been prepared from the plant.FUNGI LIKE PROTOCTISTSLIME MOLD (PLASMODIUM STAGE)

In initial stages of life cycle, slime mold are creeping masses of
living substances, having the consistency of an unboiled egg white and
the colour of the yolk.

It sends out protoplasmic arms that engulf and digest bacteria from the surface of rotten rock or leaves.

This amoeboid stage of slime mold is called plasmodium stage.

The plasmodium consists of the cytoplasm in which are embedded many nuclei, food vacuoles and undigested food particles.

Plasmodia can move along the forest floor, on to dead leaves that are bathed in sunlight.

FRUITING BODY

In dry warm environment metamorphosis in Plasmodia takes place and it changes into cluster of fruiting bodies.

Depending on the species the fruiting bodies look like golf balls,
feathers, bird cages or worm like and in a great variety of colours.

REPRODUCTION

Each fruiting body produces a large number of microscopic asexual reproductive cells known as spores.

Each spore has a single nucleus and a thick protective wall.

Germination of the spore occurs when there is plenty of water and suitable temperature.

When a slime mold’s spore germinates, it produces one or more tiny cells.

Each cell has a pair of flagella that propel it through the film of water, which is necessary for its germination.

These flagellated cells some times function as gametes (sex cells) and fuse in pairs. This is true sexual reproduction.

Fusion of the gametes forms zygote, which become amoeboid and form a new plasmodium i.e. multinucleated slime mold

PHYTOPTHORA INFESTANS(WATER MOLD)
This fungi like protoctist belongs to family Oomycotes.
It is a pathogenic organism causing. “late blight of potato”STRUCTURE

The mycellium consist of Hyphae which are endophytic, branched, aseptate coenocytic, hyaline and nodulated.

The rounded or branched hustoria are found which absorb food material from the host cells.

REPRODUCTION
Sexual as well as asexual reproductions are present.(A)ASEXUAL REPRODUCTION

The spores are produced on the branched Sporangiophore in favorable condition.

Sporangiophore coming out through the stomata, in groups on the lower surface of infected leaves.

The sporangia are produced on the branches of sporangiophore.

On maturation, the sporangia the detached from sporangiophore.

On maturation the protoplasm of the sporangium converts into uninucleate, vacuolated and naked zoospores.

When mature sporangium burst the zoospores liberate in the film.

(B)SEXUAL REPRODUCTION

Sexual reproduction is zoogamous.

The female sex organ is oogonium. while the male sex organ is antheridium.

The antherialium develops first and the oosgonium later.

Both sex organ may develop on he same Hyphae or on two adjacent Hyphae lying side by side.

The oogonium hyphae penetrates the antheridium.

The oogonium is pear shaped and contains a single female nucleus in it.

The fertilization takes place when the male and the female nuclei
fuse in the egg after penetration of the oogonium in the antheridium.

There is no fertilization tube and after fertilization the thick
walled zoospore developed, which is present inside the oogonium.

The oospore germinates in favorable conditions and produce new mycellium.

Reduction division occurs during germinates of oospore.

ECONOMIC IMPORTANCE

The Water Mold causes a disease in potato crop known as “late blight of potato”

This disease effects both aerial and underground parts and whole plant becomes blighted in severe conditions.

The disease appears in the form of brown spread patches on leaves and rapidly increases to the whole leaf surface.

The tuber converts into a rotten pulpy mass emitting foul smell and remains small in size.

A great danger to potato crop and causes sufficient damage of Potato crop.

EUGLENA
Euglena is an unicellular, flagellated organism. It belongs to the division “Euglenophyta”OCCURANCE
Euglena commonly found in drains, ponds and is also present in soil, blackish water and even salt water.DUEL NATURE

Euglena has characteristics of both animals and plants.

It is more evolved than green Algae.

STRUCTURE
1. It is somewhat elongated animal, almost pointed at both ends.
2. It has definite and easily stainable nucleus.
3. It has well defined chloroplast as in higher plants.
4. All the Euglena have two flagella usually one of them is long and the other one short by which they can swim activity.
5. They lack the outer cellulose cell wall, instead the protoplasm is bounded by a grooved layer called the “Pellicle”.
6. Euglena has a gullet near the base of the flagella and an eyespot containing a pigment called “Astaxanthin”.
7. Reproduction is usually asexuality by simple division.TAXONOMIC POSITION OF EUGLENA

One of the examples of Eukaryotes is Euglena.

Belongs to group kingdom Protactista.

PLANT LIKE CHARACTERS IN EUGLENA
1. Presence of Chloroplast.
2. Undergoes physiological, biochemical process of photosynthesis.
3. Behaves as natural autotroph in presence of sunlight.ANIMAL LIKE CHARACTERS IN EUGLENA
1. Absence of a cell wall.
2. Presence of a mouth with cytopharynx.
3. Eyespot containing animals pigment called “Astaxanthin”.
4. Presence of reservoir.
5. Can easily be converted into heterotopy after the loss of chloroplast.ANIMAL LIKE PROTOCTISTAPHYLUM PROTOZOAGENERAL CHARACTERS
1. Protozoa are microscopic, unicellular (as single cell performs all vital activities) organisms.
2. These organisms are asymmetrical.
3. The body of organism may be naked or covered by pellicle to maintain the shape.
4. Cytoplasm of protozoans is usually divided into outer, ectoplasm and inner granular endoplasm.
5. Cell may be uninucleate or multinucleate. Nuclei are covered by nuclear membrane.
6. Protozoan may be solitary or colonial.
7. They are aquatic and are found in both fresh and marine water.
8. Nutrition may be holozoic (animal like), halophytic (plant like) or
saprozoic (subsisting in dead organic matter) or parasitic.
9. Digestion is intracellular and is accomplished inside the food vacuole.
10. Locomotion takes place by flagella, cilia or psendopodia.
11. Respiration takes place through general body surface.
12. One or more contractile vacuoles are present for osmo-regulation.
13. Reproduction takes place by both asexual and sexual methods.
14. The asexual methods include binary fission, multiple fission and budding.
15. Sexual reproductive methods include gamete formation (Isogamies and Anisogamous) or by conjugation.CLASSIFICATION
About 30,000 species of protozoa are divided into five classes, which differ in their means of locomotion.
1. Class flagellate (Mastigophora).
2. Class sarcodina (Rhizopoda).
3. Class ciliate (Ciliophora).
4. Class suctoria.
5. Class sporozaa.(1)CLASS FLAGELLATA
1. Locomotary organs are long hair like “Flagella” with are one or two in number.
2. Body is enclosed in a thin covering of “Pellicle”.
3. Asexual reproduction takes place by longitudinal fission.
4. Class Flagella is divided into sub classes.(A)SUB-CLASS PHYTOFLAGELLATA (PHYTOMASTIGMA)

Contain chlorophyll and perform process of photosynthesis.

Examples: Euglena and Volvax.(B)SUB-CLASS ZOOFLAGELLATA (ZOOMASTIGMA)

Does not contain chlorophyll and are heterotrophic.

Examples: Trypanosome and Leis mania.
Some flagellates are parasites. For example: Trypanosome is a blood
parasite human and causes African sleeping sickness. Its carrier is “Tse
Tse fly”.(2)CLASS SARCODINA (RHIZOPODA)
1. Locomotion takes place by “Psendopodium”.
2. Body shape is not definite and keep on changing because the pellicle is absent. Some have external sheats or skeletons.
3. Nutrition is mostly holozoic, some are parasite. E.g. Entamoeba, histolytic can cause human dysentery.
4. Example:
i. Entamoeba histolytic is a parasite living in intestine of man. ii.
Foraminifera is a group including shelled sarcodimians. E.g.
Polystomella. iii. Heliozoa is a group including fresh water organisms
having fine, stiff and ray like psendopodia e.g. Actinophrys.(3)CLASS CILIATA
1. Locomotory organs are cilia which are short, thin, protoplasmic structure, covering the body surface.
2. Body shape is definite and maintained by pellicle.
3. Many ciliates have a groove or depression called “Gullet” into which food can be brought.
This class is divided into two sub-classes.(i) SUB-CLASS PROTOCILIATA

(4)CLASS SUCTORIA
1. They are closely related to ciliates, therefore both are includes in same sub-phylum i.e. sub phylum Ciliphora.
2. Young individual have cilia and swim about but the adults are
sedentary and have stalks by which they are attached to the substrate.
3. Body bears a group of delicate cytoplasmic tentacles, some of which
are pointed to pierce their prey, where as others are tripped with
rounded adhesive, knobs to catch and hold the prey.
4. The tentacles secrete a toxic material which may paralyze the prey.
5. Suctorians have two nuclei i.e. meganucleus and micronucleus.
6. Reproduction is by asexual budding. E.g. Acineta, Ephelota.(5)CLASS SPOROZOA
1. All are parasites.
2. Lomotary organs are absent.
3. Body covered by a thick cuticle.
4. Asexual reproduction is by multiple fission or sporulation.
5. Sexual reproduction is isogamies or anisogamous.
6. Examples.
i) Plasmodium is a human blood parasite enters the human blood when an
infected female Anopheles mosquito bites humans. Plasmodium reproduces
asexually in man and sexually in the body of mosquito.
ii) Monocytis lives as a parasites in seminal vesicles of earthworm.MALARIAINTRODUCTION
“Malaria is an infectious disease marked by attacks of chills fever,
sweating occurring at intervals that depends on the time required for
the development of a new generation of parasites in the body”.CAUSATIVE AGENT
Malaria is caused by a protozoan parasite of the genus PLASMODIUM. It was discovered by LAVERAN in 1878.TRANSMITTING AGENT
Malaria is transmitted into the blood of man by the bite of an
infected “FEMALE AND PHELES MOSQUITO”. It was discovered by KING in
1717.SYMPTOMS OF MALARIA
The symptoms of malaria first appear after several days of infection
in man. He time taken by parasite before it appears in the blood is
called INCUBATION PERIOD.SYMPTOMS DURING INCUBATION PERIOD
The symptoms that appears in incubation period:

Nausea.

Loss of appetite.

Constipation.

Insomnia.

Headache.

Muscular pain.

Aches in joint develops.

USUAL SYMPTOMS OF MALARIA

Onset of malarial fever

Shauking chills

Sweating

Rise in body temp. (may be up 106˚)

MALARIA – A BIOLOGICAL PROBLEM
Malaria has been one of the man’s most important biological problems.
Millions of people have been killed only because of his disease. To
solve this problem, various biological methods were applied to find out
in details. Experiments were performed, observation and data were
collected, and finally the complete life cycle of the malarial parasite
was studied.STUDYING MALARIA EXPERIMENTALLY
In the experimental study of malaria, several HYPOTHESIS were
presented and deductions were made for each of them. Experiments were
performed to test the deduction and observations are recorded. If the
deductions are proved true, the hypothesis regarded as correct.HYPOTHESIS (1)
A hypothesis was made about the malarial parasite plasmodium that: “Plasmodium is the cause of malaria”DEDUCTION
To test the above hypothesis, the following deductions were made: “If
the plasmodium is the cause of malaria, then the patients suffering from
malaria should have malarial parasite in their blood”.EXPERIMENT
Experiment were carried out by examining blood samples from malarial
patients that showed positive result. To prove it further experiments
were repeated whenever malaria accured.RESULT
In this way the hypothesis that the “Plasmodium is the cause of malaria” was found to be true.HYPOTHESIS (II)
It was noted that people living around the marshy places were usually
have the attack of malaria. Thus the hypothesis was stated “Malaria is
associated with marshes”DEDUCTION
To test the statements, a deduction was made that “If marshes are eliminated”.EXPERIMENT
On experimental basis, marshes were eliminated and as a result the role of infection of malaria was greatly much reduced.RESULT
It was this proved that malaria is associated with marshes. Thus the
hypothesis stands true. Thus, it is new understood that accurate methods
are essential to understood biological problems.LIFE – CYCLE OF MALARIAL PARASITEDISCOVERY
Life cycle of plasmodium in ANOPHELES MOSQUITO was first discovered in 1898.PHASES OF LIFE CYCLE
The life cycle of plasmodium is digenetic involving two phases is two hosts for completion.
1. ASEXUAL PHASE IN MAN (PRIMARY HOST)
2. SEXUAL PHASE IN MOSQUITO (SECONDARY HOST)1. ASEXUAL CYCLE IN MAN (SCHIZOGONY)INTRODUCTION
The life cycle of plasmodium in mass is Asexual and is called SCHIZOGONY, because “SCHIZONTS” are produced.PHASES OF SCHIZOGONY
According to Graham (1948), the life cycle of plasmodium can be divided into four phases;
1. PRE-ERYTHROCYTIC PHASE (LIVER SCHIZOGONY).
2. ERYTHROCYTIC PHASE.
3. POST-ERYTHROCYTIC PHASE.
4. GAMORONY OR GAMETOCYTIC PHASE.EXPLANATION OF SCHIZOGONYINFECTION
A healthy person acquires infection when a female Anopheles mosquito,
containing infective stages (SPOROZOITES) of parasite is its salivary
gland, bites him for sucking his blood.(1)PRE-ERYTHROCYTIC PHASE
Once with in the human blood, the sporozoites circulate in the blood for about half an hour.INVASION OF LIVER
After circulation in the blood, the sporozoites get into liver to invade the hepatic cells.SCHIZONT FORMATION
After penetrating the liver cells, each sporozoite grows for no. of days and becomes a SCHIZONT.CRYPTOZOITE FORMATION
SCHIZONT divides to form a large number of uninucleate CRYPTOZOITES, which are liberated when the liver cell burst.METACRYPTOZOITE FORMATION
The released cryptozoites invade the fresh liver cells and multiply producing enormous no. of metacryptozoites.(2) ERYTHROCYTIC PHASETROPHOZOITE FORMATION
The metacryptozoites after escaping into the blood stream, invade the
red blood corpuscles. Each become rounded and is called TROPHOZOITE.SIGNET RING STAGE
When trophozoite grows in size, the nucleus is pushed to one side into
the peripheral cytoplasm. It resembles a signet ring and is preferred to
an SIGNET RING STAGE.MEROZOITE FORMATION
The trophozoite ingesis a large amount of cytoplasm of the R.B.C. The
blood H6 is broken down into its protein components, which is used by
trophozoite develops into an active amoeboid trophozoite. After active
feeding, it becomes rounded and grows in size and become and SCHIZONT.
It now undergoes SCHIZOGONY and produces MEROZOITES.RELEASE OF MEROZOITES IN BLOOD
With the rupture of RBC’S, the merozoites are liberated into the blood
plasma. These invade fresh corpuscles to repeat the cycle. The time
taken to complete one erythrocytic cycle depends upon the species of
Rasnodium.(3) POST-ERYTHROCYTIC PHASE
Some merozoites produced in erythrocytic phase reach the liver cells and
undergo schizonic development. This is known as Post-Erythrocytic
Phase.(4) GAMOGONYFORMATION OF GAMETOCYTES
When successful asexual multiplication is achieved, the merozoites donot
proceed further with the erythrocytic phase but, after entering the
RBC, increase in size to form Gamocytes.TYPES OF GAMETOCYTES
Gametocytes are of two types:
1. Male Microgamo Cycle
2. Female Macrogamo Cycle
The Gametocytes do not divide, but remain within the host blood until
they are injected by the vendor, in which they continue their sexual
development.SEXUAL CYCLE IN MOSQUITOINTRODUCTION
Sexual life cycle of Plasmodium is completed in the gut of Female
Anopheles Mosquito resulting in infective Sporozoites. This cycle is
completed in 12-23 days.PHASES OF SEXUAL CYCLE
This cycle comprises of following stages:
1. Gametogony
2. Syngamy or Fertilization
3. SporogonyEXPLANATION OF SEXUAL CYCLE(1) GAMETOGONY
Gametogony refers to the Formation of Gametes. The gamocytes are taken
up along with the blood into the stomach of the mosquito and develop
into gametes.FEMALE MACROGAMETE
The female gamocytes soon become macrogamete, which is larger in size and ready to fertilize.MALE MICROGAMETE
Each male gamocyte forms 6 to 8 sperms like microgametes by a process of Exflagellation.(2) SYNGANY OR FERTILIZATIONZYGOT FORMATION
Within the gut of mosquito the two gametes of opposite sexes fuse together to form a zygot. This process is called Syngamy.OKINETE FORMATION
After fertilization zygot differentiates into motile worm-like ookinete.OOCYST FORMATION
Ookinete penetrates the stomach wall to settle down just under the mid
gut. Here after observing nutrients, it develops a cyst around it and
becomes spherical. This encysted is called Oocyst.(3) SPOROGONY
The oocyst then enters a phase of asexual multiplication, the Sporogony.SPOROBLAST FORMATION
In 6 to 7 days, the nucleus of oocyst divides into several nuclei and
cytoplasm envelops each one of them and thus hundreds of oval shaped
Sporoblasts are formed.SPOROZOITE FORMATION
The sporoblast nucleus again divides and forms hundreds of filamentous,
uninucleated Sporozoites. The cyst bursts and liberated sporozoites
migrates to the Salivary Gland where they await to penetrate to a human
host.

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